I remember reading a blogpost a while ago linked from this subreddit along the lines of "The true cost of storage is a lot more than you think" and it illustrated this with an example like this.

Let's say you have 1 TB of data you want to store. Well, to do a 3-2-1 backup you'll need 3 copies of that data, so now for 1 TB of storage you'll need 3 terabytes. And now you'll have to double that for Raid X, and now you should also have about 30% extra space for some expansion without having to buy more, so now you add 30% to 3 TB and now you double it again..."

And it goes on like this, and it ends up with something like 15 Terabytes to store 1 TB of data effectively. I'm fuzzy on the details though, as shown in my example.

Does anyone have the link to something along this line of thinking? Nothing comes up when I Google variations of how much storage you need for a given set of data. Anyone know how the rule of thumb goes?

Thanks!